Well, I just wanted to report that today I wasn't feeling "up to" fasting (only one day between fasts this week) but I decided to experiment and just drink tea, milk and coffee all day and have all my calories in the evening..... and not a migraine in sight!
I'm so pleased. I'm not woozy or even overly hungry. I have a slight tingly headache but I suspect that will go when I have my lovely 400 cal dinner.
So, if you get migraines with 5:2 - don't worry, there's hope!